An effective method of separating proteoglycans from extracts of rabbit corneas, which has been developed in this laboratory, will be applied to metabolic studies. Corneas will be maintained in organ culture while various labeled precursors are incorporated into the proteoglycan structures. Sulfate, hexosamines, and amino acids will serve as radioactive precursors. The extracted proteoglycans will then be separated, and the relative rates of labeling of their polysaccharide and protein components will be determined. Any evidence of precursor/product relationships among the proteoglycans will be sought. If the corneas can be maintained long enough in a healthy metabolic state, pulse-chase labeling experiments may permit measurement of turnover rates.